1. Field of the Invention
The present invention relates to an ink circulation apparatus, an ink circulation method, and an inkjet recording apparatus, and particularly to a technique of preventing a defected nozzle of the inkjet head from being generated.
2. Description of the Related Art
In the inkjet recording apparatus, if bubbles or dissolved gas exists in ink, the ink may not be sufficiently compressed when being ejected, so the ejection property is decreased, and the ink flow is not stable. Accordingly, dot omission or defective printing may occur.
In order to solve the problems above, in JP1993-17712 (JP-H5-17712), a technique of transmitting dissolved gas in ink through a layer having a transmitting property and removing the gas is disclosed. According to the technique, gas can be easily removed even from ink generating bubbles and ink having a volatile component.
Meanwhile, it is known that in radical polymerization-type UV-curing ink, when removing gas from the ink, an oxygen amount in the ink is decreased and the ink is thickened (viscosity is increased)(JP2008-132701).
In order to prevent the radical polymerization-type UV-curing ink from being thickened, JP2006-110780 discloses an inkjet recording apparatus, that includes a gas removing unit that removes dissolved gas from ink supplied to an ink chamber and a gas supply unit that supplies gas to the ink supplied to the ink chamber. When the inkjet head performs the ejection operation, the gas removing unit is driven and controlled so that ink from which the dissolved gas is removed fills the ink chamber, and when the inkjet head does not perform the ejection operation, the gas removing unit is driven and controlled so that ink to which gas is supplied fills the ink chamber.
According to the technique, if the inkjet head performs the ejection operation, the ink from which the dissolved gas is removed fills the ink chamber, so bubbles caused by dissolved gas in the ink chamber can be suppressed from being generated. If an inkjet recording apparatus does not perform the ejection operation, the ink to which gas is supplied and in which dissolved gas is increased fills the ink chamber, so the ink in the ink chamber is not easily cured, and particles caused by the cured ink can be suppressed from being generated.